Musicians having to learn and prepare a new program every week, often feel guilty about the time that they don’t spend preparing adequately.
What is the best way to prepare for a new program? After 10 years of playing in a full time orchestra you have probably played most of the classical repertoire, a great deal of the contemporary, and a portion of the modern. However, it often feels as though we are learning the part for the first time. For the most part, difficult parts need to be relearned. I found ways to save enormous preparation time and it has become even easier with internet and streaming. The greatest for me is Naxos which has almost any classical work imaginable available for streaming at a reasonable cost. http://www.naxos.com/ The biggest drawback is that you can’t save the file.
Listening to as many varying recordings, and as early as possible for the given program, while still doing other things, cuts the learning time at least by half for me. It also helps me enjoy the works more during rehearsal week as well. The feeling of not only being prepared technically but also musically makes the whole experience many times fuller than imaginable.
Listen to the works while still being productive, doing chores, traveling, working or eating. Begin as early as possible, at least 2 weeks in order to give yourself a good week before the first rehearsal to practice your parts.  Many of us read well enough that we could get away with not practicing but there is no doubt that you will do a much better job and enjoy it more if you prepare properly. Good luck and love the music.